India is predominantly an
agrarian country with nearly three fourths of the people
dependent on agriculture or rural economy. The most outstanding
achievement of Indian agriculture since independence is the
phenomenal growth of foodgrains output. During the last three
decades, Indian agriculture has experienced a revolutionary
breakthrough in foodgrain production leading the country from
deficit and import arena to the positive situation of
self-sufficiency and buffer stocks. The foodgrain production in
the country increased from 50.8 million tonnes in 1950-51 to
152.37 million tonnes in 1983-84, but the growth of Indian
agriculture still continues to be linlked with the vagaries of
nature. Some of the states in the country have come across the
unprecedented draught of the century for the fourth successive
year which has caused tremendous hardship to the people as also
loss of production of foodgrains in those states.

Nearly seventy percent of the
total production of foodgrains in India is retained at farm level
where the unscientific and faulty storage conditions enhance the
chances of fungal attack and thereby mycotoxin production. The
decomposers of foodgrains i.e. fungi, bacteria etc. are always
present on foodgrains in dormant conditions (usually as spores)
and grow under favourable climatic and other conditions (1). The
fungal growth may cause decrease in germinability, discolouration
of grain, heating and mustiness, loss in weight, biochemical
changes and production of toxins. All these changes may occur
before the responsible fungi could be detected on visual
examination (2).

The fungi produce a large number
of mycotoxins in foodgrains and their products. Mycotoxins are a
group of highly toxic secondary metabolises of the fungi produced
under certain favourable environmental conditions (3). Because of
their potent toxic nature and fairly common occurrence under
natural conditions, mycotoxins have attracted world-wide
attention in the recent years. The diseases or physiological
abnormalities resulting due to ingestion of mycotoxins are known
as "mycotoxicosis" (4).

2. GENESIS OF THE PROBLEM

Association of mould produced
toxins with food commodities has been knowri since Biblical times
but their role in inciting disease syndrome was realised only
when it was discovered that "ergotism" was caused due
to consumption of barley and rye infected with Claviceps purpurea
(5). Cardiac beriberi caused by Penicillium citreovirde was
recorded in Japan due to consumption of contaminated rice;
Stachybotryotoxicosis of horses in Soviet Union in 1931; Red
Mould Diseases or Black Spot Diseases Caused by Fusarium sps. in
Japan during 1940-50 and Alimentary Toxic Aleukia (ATA) caused by
Fusarium and Cladosponum species in USSR during 1942-47 (6).

The severity of mycotoxin problem
was realised during World War II when Russians eating mouldy
overwintered grains sufferred with severe dermal necrosis,
leukopenia, haemorrhages and destruction of bonemarrow._ Fusarium
was found to be the causal organism (7). World-wide scientific
recognition of mycotoxin problem was, however, only in 1960 when
it was discovered that the aflatoxins were responsible for the
death of about a lakh turkey poults (Turkey x disease) in England
(8). According to Blount, the "poisonous feed" which
caused the havoc and which was the preparation of Brazilian
peanuts, was contaminated with Aspergillus flavus (9).

3. NATURAL OCCURRENCE OF MYCOTOXINS IN INDIA

Cereals constitute the most
important food and feed sources which are affected by various
mycotoxic fungi. The problem of natural occurrence of mycotoxins
in cereals aggravated to some extent due to rapidly changing
agricultural technology (10). In general, mycotoxins and
particularly aflatoxins seem to pose great problem in the tropics
than in the temperate regions but no part of the world can be
considered to be mycotoxin-free zone due to the movement of
various foodstuffs from one part of the globe to the other (4).

Some of the important commodities
which have been found to be naturally contaminated with one or
the other mycotoxins are listed below:

3.1 Maize:

Maize is an excellent substrate
for mould growth and mycotoxin production. In India, systematic
survey of maize grains for mycotoxins contamination has been
undertaken in some parts only. However, some reports mainly on
aflatoxin contamination in stored grains have indicated that the
problem of aflatoxin contamination is much more serious than
usually visualised (4). In an extensive survey of the important
maize growing areas of Bihar, natural contamination of mycotoxins
and particularly of aflatoxin was reported in the grains of field
maize crop (11). Surveys conducted by the Indian Grain Storage
Institute during 1978-79 and 1980-81 indicated contamination of
stored maize grain samples with aflatoxin B1 in the range of
40-510 ppb (12,13).

Under a FAO sponsored Food
Contamination Monitoring Project, out of 10 maize samples
collected from Western Uttar Pradesh, 3 samples were found
contaminated with aflatoxin B. in the range of 20-80 ppb (14).
Samples of maize collected from traditional storage structures
from various parts of India have shown contamination of aflatoxin
B1 in the range of 15680 ppb (15). Fifteen varieties of maize
were screened by Bilgrami et al (16) for aflatoxin production by
artificial inoculation of A. parasiticus. Practically ail the
varieties favoured aflatoxin production, but in varying degrees.
Maize is a good substrate for the production of Zearalenone which
has been detected frequently in commercial varieties. Reports of
natural occurrence of Zearalenone in standing maize crop are also
available (4).

3.2 Rice:

Rice is also one of the important
cereals which favours mycotoxin production. Natural occurrence of
aflatoxin and aflatoxin producing fungi in rice has been reported
from various parts of the world (16). In a survey of paddy
harvested from rain affected crop in Punjab and Haryana, out of
83 samples only 3 ewre found contaminated with aflatoxin B. in
the range of 10-40 ppb (17,18). Rice stored for prolonged periods
i.e. 4-8 years has also been reported to be contaminated with
aflatoxin B. in various parts of India (12, 13, 14, 15, 10, 20,
21).

Presence of some other mycotoxins
like citrinin, Sterigmatocystin and Ochratoxin has been detected
as natural contaminants of rice in one or the other region of the
world. Only scanty information is available pertaining to these
toxins in India (4).

3.3 Wheat:

Wheat does not appear to be a
good substrate for aflatoxin elaboration. Survey reveals that
natural contamination of wheat occur but in low profile (30). Out
of 223 samples collected from wheat growing belt of Western U.P.
(India), only 9 samples were found contaminated with aflatoxin B.
in the range of 8-40 ppb (4,19,22). In 1985, all the six flood
affected wheat samples collected from Punjab were found
contaminated with aflatoxin B1 in the range of 8-40 ppb (24).
There are few other reports of the natural contamination of
aflatoxins in wheat in India (23, 31). Reports of natural
occurrence of Sterigmatocystin in the domestic and imported red
& white wheat are also available from India (32).

3.4 Barley, oats, millets etc.:

Like wheat these small grains
also do not favour natural contamination of mycotoxins. However,
some of these grains have been reported suitable substrates for
aflatoxin production. All the four aflatoxins B1, B2, G1, G2 as
natural contaminants were isolated from sorghum grains obtained
from ears affected by A. flavus in North India (25). In Western
India sorghum samples were found contaminated with aflatoxin B.,
the level of which was significantly correlated with moisture
content as well as A. flavus population (26). A survey in Central
U.P. (India) has indicated that sorghum and bajra are also
naturally contaminated with aflatoxin B. during storage (19). It
was also noticed that contamination of aflatoxin degraded
quantity-wise with the increase in storage period during May to
September. Perhaps, it was because of the fact that the
production of aflatoxin diecreases with increase in the
temperature beyond 25°C. Out of the total contaminated samples,
only 2 samples of sorghum contained 40 ppb, beyond the prescribed
limit of 30 ppb for food in India.

3.5 Pulses & Oilseeds:

A survey under FAO sponsored Food
Contamination Monitoring Project in Western Uttar Pradesh
revealed that few samples of pulses including green gram, black
gram & lentil and few samples of cotton seed were found
contaminated with aflatoxin B1. The range being 4-80 ppb in
pulses and 35-200 ppb in oilseeds (14). Similarly, ten percent of
stored soybean samples were found contaminated with aflatoxin B.
in the range of 4-40 ppb, in a survey in Uttar Pradesh (27).

A survey carried out by the
Central Food Technological Research Institute, Mysore and
Regional Research Laboratory Hyderabad revealed that 80 percent
of the peanut meal produced in different states in India was
found contaminated with aflatoxin at varying levels (28).

3.6 Dry fruits & spices:

Aflatoxin has been reported as
the main contaminant of coconut and other dry fruits viz. almond,
cashew nut, walnut, raisin, makhana and emblic. In some samples
of these dry fruits, presence of Zearalinone, Citrinin and
Ochratoxin has also been reported. Natural contamination of
aflatoxin in various samples of chillies, fennel, cumin,
coriander, black pepper, ginger, cardamom and turmeric and
presence of Orchratoxin, Citrinin and Zearalinone has also been
reported in a few samples of spices (33). In a limited survey in
Uttar Pradesh conducted by the Indian Grain Storage Institute,
Hapur during 1984-85, it was revealed that out of 99 dry fruit
samples only 19 samples were contaminated with aflatoxin B1 in
the range of trace to 50 ppb (19).

3.7 Milk & Milk Products:

Milk and milk products are
consumed by the people of all age groups and are also important
sources of mycotoxin exposure. So far no systematic survey of
milk or milk products has been done in India (33). Some reports
indicate that aflatoxin M, upto 8 mg/l were detected in the milk
of buffaloes in Andhra Pradesh (34).

3.8 Cattle & Poultry Feed:

Cereals and oilseeds constitute
more than 70 percent fraction of cattle and poultry feed.
Usually, the food which is declared unfit for human consumption
finds its way as feed for animals and poultry birds (33). A
number of reports indicated the presence of high concentrations
of aflatoxins as natural contaminants in cattle feed. Presence of
Ochratoxin A and Sterigmatocystin has also been shown in some
samples of cattle feed containing sunflower cake and green gram
(35).

4. HIGH RISK AREAS IN INDIA

Being aerobic in nature,
mycotoxic fungi require air, moisture, nutrients and suitable
temperature for their growth and metabolism (4). Moisture content
of the grain or the relative humidity surrounding the substrate
are the most important factors governing the growth and aflatoxin
production by A. flavus. Climatic conditions in India are most
conducive for mould invasion proliferation and elaboration of
mycotoxins. The high risk areas identified in India are Kerala,
Western India, Gangetic plains, north eastern as well as coastal
areas of Andhra Pradesh, Karnataka and Tamil Nadu (16).
Unseasonal rains, flash floods are very common in India which
enhance the moisture content of the grain making them more
vulnerable for fungal attack (30).

5. PROBABILITIES OF CONTAMINATION

Warm humid climate provides
congenial atmosphere for the growth of fungi and production of
toxins. Aspergillus flavus which is known as storage fungi may
infect and produce aflatoxins in crops in the fields also (30).

Foodgrains are normally harvested
at higher moisture content and then dried to bring down the
moisture content up to safe level before storage. Delay in drying
to safe moisture levels increases risks of mould growth and
mycotoxin production.

Natural calamities like floods or
torrential unseasonal rains during pre, mid or post-harvest
stages may render the crops vulnerable to microbial attack.
Annual loss due to spoilage of high moisture paddy is
conservatively estimated to be 10-15% of the total production of
paddy, produced during rainy season in India (22).

Faulty storage conditions may
also enhance the chances of microbial attack and production of
mycotoxins. Thus, starting from harvesting of the crop till the
food or food products are consumed by the consumers, there are
chances of microbial invasion/fungal attack at each and every
stage/step.

6. R & D CENTRES FOR STUDY OF MYCOTOXINS IN INDIA

Considerable R & D work on
mycotoxin contamination is being carried out at the following
centres:

National Institute of
Nutrition (NIN), Hyderabad.

Central Food Technological
Research Institute (CFTRI), Mysore.

Indian Grain Storage
Institute (IGSI), Hapur.

Central Drug Research
Institute (CDRI), Lucknow.

Industrial Toxicology
Research Centre (ITRC), Lucknow.

Vallabh Bhai Patel Chest
Institute, New Delhi.

Universities/Regional
Research Laboratories under the CSIR.

I.C.A.R. and its Centres.

7. REGULATIONS

Eighteen countries all over the
world have guidelines or regulations which prescribe maximum
acceptable limits for aflatoxins in food and feeds.

The limits prescribed vary from 0
to 50 ppb in foods and from 0 to 1000 ppb in feeds (30). The
Protein Advisory Group of United Nations has recommended intake
maximum 30 ppb aflatoxin in foods rich in protein, where use of
contaminated food cannot be avoided.

In India, the Governmental
agencies procure foodgrains confirming to prescribed
specifications thereby minimising the chances of contamination
and thus ensure the supply of good quality foodgrains to the
consumers through PDS. At farm level also quality consciousness
is created amongst the farmers through a network of 17 teams of
Save Grain Campaign. These teams educate, motivate and persuade
the farmers to adopt scientific methods of foodgrains storage
with a view to minimise the qualitative and quantitative losses
in foodgrains during storage likely to occur due to insects, rats
and moulds. The Quality Control Teams monitor the quality of
foodgrains at commercial level.

8. PREVENTION AND CONTROL OF MYCOTOXINS

Hazards of mycotoxin infected
food are now well recognised. Considerable concern has,
therefore, been shown in the recent years towards the control of
these toxic metabolises. Control is attained by preventing the
growth of moulds, separation of infected grains, detoxification
and by growing resistant varieties (33).

8.1 Prevention of mould growth:

In stored grain, mould damage may
be prevented mainly by three kinds of methods viz. drying of
grain, controlled atmosphere storage and chemical treatment.

8.1.1 Drying of grain: It is an established fact that dry grain
stores long, safe from insects and moulds because the
requirements of moisture for their development are not met. The
average Indian farmer perform drying of grain conventionally
under direct sun light (36). The most widely used indigenous
practice of grain drying is to spread threshed grains in thin
layers on Kachcha floor with cow-dung in the open sun and
stirring it by human labour till the grains are dried to safe
level. Some farmers have also been using Pucca floors. Sun drying
of grains on Kachcha surface was quicker as compared to Pucca
surface, transparent polythene & black polythene. 5.30
percent loss in the moisture content of maize dried in sun-light
could be achieved during 8.5 hours time (36). Exposure of
aflatoxin contaminated groundnut oil to sun light has given very
promising results as it destroyed about 99 percent of the
aflatoxins (4). Other methods of grain drying include mechanical
drying, in-bin drying, infrared, microwave or sonic and solar
energy drying. Researches are being conducted to employ these
methods also (37).

81.2 Controlled atmosphere storage: The significance of underground storage
lies behind the philosophy of grain cooling and depleting the
oxygen content to the desired level whereby the microbes and
insects cannot grow. Air-tight storage also works on the same
phenomenon where the depletion of oxygen by grain respiration
manipulates disinfection by inhibiting aerobic fungi, elimination
of mycotoxin production and conservation of desirable quality
factors in the grain. Natural cooling is another effective method
of preserving grain. The low temperature does not allow the
microflora to grow as most of them are thermophillic.

8.1.3 Chemical treatment: Chemical control of fungal deterioration
to stored grain is restricted to the treatment of grain for seed
purposes only but not for food and feed. Experiments conducted by
Indian Grain Storage Institute showed that "Grain
treat" (Mixture of propionic acid, acetic acid and benzoic
acid) against Aspergillus & Penicillium sps. did not produce
effective results in maize. Seed treatment with Bavistin and TMTD
(Trimethyl thiuram disulphide) at 0.25 per cent concentration
gave 100 per cent protection to wheat grain in one year storage
against Aspergillus and Penicillium sps (37). Certain mild
phenolics like perulic acid and O-Vanillin have also been
reported to prevent aflatoxin production on rice, wheat, maize,
groundnut and mustard seeds (33).

8.2 Separation of infected grains:

Physical separation of infected
grains is an efficient and feasible method of minimising
mycotoxin contamination. This is effected either by manual
operation or with the help of an electronic sorter. Fungal
infection of seeds or grain usually imparts characteric colour or
other physical properties.

8.3 Detoxification:

Cooking at atmospheric pressure
can destroy about 50 percent of the toxins. Dry roasting and oil
roasting of groundnut reduces aflatoxins to a significant degree.
Cooking rice under 15 Ibs. pressure for 5 minutes gave maximum
destruction of aflatoxins (72 percent) as compared to ordinary
cooking or cooking with excess water. Light has also been
employed successfully to destroy aflatoxin in crude groundnut
oil. Studies have shown that visible light is more effective than
either ultra-violet or infra-red light (30).

8.4 Growing resistant varieties:

In view of the hazardous effects
of mycotoxins, efforts are being made to develop mould resistant
varieties which will be mould free not only in fields as standing
crops but during storage also they will restrict development of
moulds.

List of important mycotoxins,
producer fungi and principal toxic effects

Srivastava, J.L. (1987).
Mycotoxin problems in food in India. Paper presented at
the Joint FAO/WHOIUNDP Second International Conference on
Mycotoxins held at Bangkok, Thailand from September
28-October 3,1987.